The present invention relates to a new and improved construction of a yarn or thread tension compensating apparatus for a winding device of a textile machine, typically a winding or spooling machine, which is arranged between a take-off roll and a take-up bobbin having operatively associated therewith a yarn traversing device.
In the context of this disclosure the term "yarn" as used herein is employed in its broader sense as encompassing not only yarns, but threads and other filamentary material of the type normally processed at a textile machine, especially a winding or spooling machine.
The yarn tension compensating apparatus of the invention is generally of the type which is provided with a deflecting roll connected with a lever or lever means for compensating variations in the tension of the yarn which are produced by the yarn traversing or reciprocating motion.
During the winding process at winding machines the yarn is conventionally traversed to-and-fro. During such traversing movement there automatically occurs a periodic variation in the length of the yarn path through which the yarn travels. This is so since the distance between the take-off roll, or, the last guide roll, as the case may be, respectively, and the lateral end of the bobbin package is greater than the distance to the center of the bobbin package. This length variation and the yarn tension variations produced as a result thereof, usually are compensated by guiding the yarn over a yarn tension compensating device arranged between the take-off roll and the bobbin package. State-of-the-art yarn tension compensating devices comprise a deflecting roll connected to a pivoting arm. This deflecting roll can be freely moved along the pivoting path. Depending upon the momentary yarn tension, i.e., depending upon the momentary position of the yarn traversing device, the deflecting roll is pivoted to a greater or lesser extent out of its idling position towards which it tends to move under the action of a restoring force exerted, for instance, by a counterweight or a spring. Such prior art yarn tension compensating devices are associated with the drawback that at high winding speeds, and thus, necessarily at high yarn traversing frequency of the yarn traversing device, the deflecting roll tends to uncontrollably vibrate under the influence of inertia forces.
A proposal for alleviating this drawback has become known to the art from Japanese Utility Model Publication No. 47-19552 which teaches a yarn tension compensating device using a pivotable double-arm lever which is pivotably mounted about a pivot point which is spatially fixed. At one lever arm of the pivotable double-arm lever there is carried the deflecting roll and at the other lever arm there is supported a counterweight. At the side carrying the counterweight the lever arm additionally is attached to two springs situated opposite one another and fixed to the machine frame. In this way, each deviation of the deflecting roll is dampened by the correspondingly counteracting spring. Nonetheless at high wind-up speeds the deflecting roll still uncontrollably vibrates.